What is the clinical evidence from this study?

Study design: Observational. Population: Left bundle branch block-induced cardiomyopathy (n=6). Intervention: Cardiac resynchronization therapy vs. Baseline (pre-CRT). Primary outcome: Mean LVEF (p=0.027).

What question did this study set out to answer?

This study aims to clarify the existence and outcomes of left bundle branch block (LBBB)-induced cardiomyopathy treated with cardiac resynchronization therapy (CRT).

June 18, 2026

Resolution of Left Bundle Branch Block–Induced Cardiomyopathy by Cardiac Resynchronization Therapy

Key Result

Cardiac resynchronization therapy significantly increased mean LVEF from 31% to 56% (p=0.027) and resolved mechanical dyssynchrony in patients with LBBB-induced cardiomyopathy.

Key Points

This study aims to clarify the existence and outcomes of left bundle branch block (LBBB)-induced cardiomyopathy treated with cardiac resynchronization therapy (CRT).
375 candidates for CRT screened between 2007 and 2010.
Included patients had a history of LBBB for over 5 years with significant LV dysfunction.
Super-response to CRT defined as LVEF >45% and improved NYHA class after 1 year.
The syndrome was diagnosed in 6 patients with an average age of 50.5 years.
Mean LVEF increased from 31 ± 12% to 56 ± 8% (p = 0.027) post-CRT.
NYHA functional class declined and mechanical dyssynchrony was nearly resolved.

Study Design

Type

Observational (n=6)

Structured PICO

Does cardiac resynchronization therapy reverse left ventricular dysfunction in patients with isolated LBBB-induced cardiomyopathy?

Population

6 patients with isolated left bundle branch block and progressive left ventricular dysfunction successfully treated by cardiac resynchronization therapy, evaluated at 1 year.

Exposure

Cardiac resynchronization therapy (CRT)

Outcome

Super-response to CRT defined as LVEF >45% and decrease in NYHA functional class at 1 yearcomposite

This study provides evidence for a specific LBBB-induced cardiomyopathy in humans that is reversible with cardiac resynchronization therapy.

Main Result

Absolute Event Rate: 56% vs 31%

p-value: p=0.027

Limitations

Retrospective design
Prevalence, time course, and risk factors need to be prospectively studied

Abstract

OBJECTIVES: The study sought to describe a specific syndrome characterized by isolated left bundle branch block (LBBB) and a history of progressive left ventricular (LV) dysfunction, successfully treated by cardiac resynchronization therapy (CRT). BACKGROUND: Isolated LBBB in animals causes cardiac remodeling due to mechanical dyssynchrony, reversible by biventricular stimulation. However, the existence of LBBB-induced cardiomyopathy in humans remains uncertain. METHODS: Between 2007 and 2010, 375 candidates for CRT were screened and retrospectively included in this study if they met all criteria of a pre-defined syndrome, including: 1) history of typical LBBB for >5 years; 2) LV ejection fraction (EF) >50%; 3) decrease in LVEF to 45% and decrease in NYHA functional class at 1 year. RESULTS: The syndrome was identified in 6 patients (1.6%), 50.5 years of age on average at the time of LBBB diagnosis. HF developed over a mean of 11.6 years. At the time of referral, Doppler echocardiograms showed major mechanical dyssynchrony at left atrioventricular, interventricular, and left intraventricular levels. During CRT, NYHA functional class decreased, LV dimensions normalized and mechanical dyssynchrony was nearly resolved in all patients, and mean LVEF increased from 31 ± 12% to 56 ± 8% (p = 0.027). CONCLUSIONS: These observations support the existence of a specific LBBB-induced cardiomyopathy resolved by CRT. Its prevalence, time course, and risk factors need to be prospectively studied.

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